1. Field of the Invention
The present invention relates to the chemical destruction of arsenic-containing organic waste or chemical agents, such as Lewisite, with simultaneous recovery of pure arsenic.
2. Description of Related Art
The destruction or neutralization of organic compounds containing arsenic presents a challenge due to the high toxicity and volatility of arsenic and its compounds. Arsenic-containing organic compounds are used as pesticides, herbicides, and less conventionally as chemical warfare agents. The destruction of these compounds is desirable to reduce storage of hazardous waste and to demilitarize stockpiles of chemical warfare agents.
Methods for detecting the presence of toxic chemical agents and decontaminating articles in contact with these agents have valuable industrial and military applications. Various methods have been devised to deactivate or decontaminate dangerous nerve and blister agents, including those containing arsenic. For example, U.S. Pat. No. 4,842,746 discloses a method for removing chemical nerve and blister agents from a cleaning solvent by preferential adsorption. U.S. Pat. No. 4,744,917 discloses the preparation and application of toxic chemical agent decontamination emulsions. U.S. Pat. No. 4,784,699 discloses a process for decontaminating military nerve and blister agents by contacting with gaseous ozone or chlorine dioxide to oxidize the agents to non-toxic products. These methods, however, do not destroy the offending compound.
U.S. Pat. No. 4,631,183 does disclose a two-step process for the destruction of toxic organic halogenated substances, including arsenic compounds. The first step is performed in a reaction chamber under a reductive atmosphere and at high temperatures (1000.degree. C.-1600.degree. C.) in the presence of an alkali or alkaline earth metal generated in situ. The second step is the oxidation of the resulting products, such as carbon monoxide.
The latter method and other standard hazardous waste destruction methods, such as incineration or molten salt destruction, are based on oxidation of the waste and can be very efficient, easy to implement, and economical. Applying these methods to the destruction of arsenic-containing organic compounds, however, is environmentally unacceptable. Typical oxidative processes operating at high temperatures tend to disperse the toxicity. Incineration, in particular, releases hazardous substances containing arsenic and also fails to recover the pure form, which is a valuable product.
The use of any oxidative destruction process, such as incineration, with arsenic-containing compounds will produce arsenic oxide in the final waste. Arsenic oxide is difficult to dispose of in large quantities, even assuming it can be trapped. To convert the oxide to a useful chemical, the arsenic must be separated from other components of the waste and then reduced to its pure form. This purification process is costly.
A more efficient process for destroying these compounds is needed. An ideal treatment of arsenic-containing organic compounds would not only destroy the compound, but also separate arsenic from the final waste in a pure form. Pure arsenic can be used as raw material for the manufacture of gallium arsenide, which is used to make semiconductor devices.